The invention relates to novel decongestant/expectorant compositions containing two essential ingredients phenylephrine tannate and guaifenesin.
A considerable number of tannic acids occur in nature. Chemically, these acids are described as polymers of different hydroxybenzoic acids. Generally, when the term tannic acid is employed, as in the present case, the acid referred to is gallotannic acid. The internal ester of gallic acid also frequently referred to as tannin.
Tannic acid consists of an amorphous powder, glistening scales, or spongy masses varying in color from yellowish-white to light brown. Tannic acid is very soluble in water or alcohol.
Tannic acids are usually obtained from glycosides which consist of several molecules of a tannic acid in combination with glucose.
Commercially available, tannic acid, also known as tannin, has a complex non-uniform chemistry, usually contains from about 5% to about 10% water by weight, has a molecular weight of about 1700, and is typically produced from Turkish or Chinese nutgall.
Phenylepherine, known chemically as 1-m-hydroxy-xcex1-[(methylamino)methyl] benzyl alcohol, is a synthetic, optically active sympathomimetic amine which has one hydroxyl group on the benzene ring. The hydroxyl group is placed in the position meta to the aliphatic side chain. The meta position affords optimal activity and phenylepherine (neo-synephrine) replaced an older preparation, synephrine, in which the hydroxyl was in the para position.
Phenylephrine hydrochloride is available in the form of the levorotatory isomer, a white, odorless, non-hygroscopic, crystalline compound possessing a bitter taste. Phenylephrine hydrochloride has a melting point of 140-145xc2x0 C. and is freely soluble in water and alcohol. Decongestant compounds in the form of their free bases as well as their salts, e.g. hydrochloride, citrate, maleate, tannate, etc., are well known. Decongestants in the form of their tannate salts are very desirable because such salts are generally stable.
Decongestants in the form of their tannate salts are typically prepared by reacting the free base, e.g. phenylephrine, etc. with tannic acid in the presence of a volatile solvent, usually isopropanol. Typically, in the conventional isopropanol route, the decongestant free base and the tannic acid will be present in the isopropanol at a concentration of about 20% based on the weight of the reaction mixture. The reaction mixture is stirred for about one hour while maintaining the mixture at 60-70xc2x0 C. The reaction mixture is cooled to room temperature and then filtered, washed with isopropanol and then vacuum dried. Alternative routes to the tannate salts are described in U.S. Pat. No. 5,599,846 and U.S. Pat. No. 5,663,41 5.
Guaifenesin, known chemically as 3(2-methoxyphenoxy)-1,2-propanediol, is a crystalline powder soluble in water and alcohol. It is indicated in the USP Drug information as an expectorant for the symptomatic relief of cough due to colds and minor upper respiratory infections.
It has now been found that the novel combination of phenylephrine tannate and guaifenesin produces a composition possessing sympathornimetic decongestant and expectorant properties superior to the use of either one of the compounds alone. Guaifenesin has an expectorant action which increases the output of respiratory tract fluid by reducing adhesiveness and surface tension. The increased flow of less viscous secretions promotes ciliary action and facilitates the removal of mucus. This changes a dry, unproductive cough to one that is more productive and less frequent.
The compositions described herein are designed to be taken twice a day with the immediate expectorant action of guaifenesin and the prolonged decongestant action of phenylephrine tannate. The compositions of the present invention may be prepared for oral administration in the form of powders, capsules, elixirs, syrups and the preferred forms of tablets or suspensions.
Tablets containing the unique phenylephrine tannate and guaifenesin compositions of the present invention are prepared in a conventional manner by the addition of suitable pharmaceutical carriers including fillers, diluents, colorants, lubricants and the like, as well as conventional and well known binding and disintegrating agents. Each tablet would contain approximately 20 to 30 mg of phenylephrine tannate and 100 to 300 mg of guaifenesin. A typical tablet composition of the present invention containing starch, dibasic calcium phosphate, colorants, magnesium stearate, methylcellulose, polygalacturonic acid, povidone and talc, as described in Example 1 which follows, is prepared by well known conventional tabletting techniques such as those disclosed in U.S. Pat. Nos. 3,018,221; 2,798,024 arid 2,757,124.